US20080272996A1 - Display system and compensation circuit thereof - Google Patents

Display system and compensation circuit thereof Download PDF

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Publication number
US20080272996A1
US20080272996A1 US11/945,997 US94599707A US2008272996A1 US 20080272996 A1 US20080272996 A1 US 20080272996A1 US 94599707 A US94599707 A US 94599707A US 2008272996 A1 US2008272996 A1 US 2008272996A1
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signal
pulse
duty cycle
display system
voltage level
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US11/945,997
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Yu-Hsiao Wu
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Qisda Corp
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Qisda Corp
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Publication of US20080272996A1 publication Critical patent/US20080272996A1/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H05B41/3927—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/04—Display protection
    • G09G2330/045—Protection against panel overheating

Definitions

  • the invention relates to a display system, and in particular relates to a compensation circuit of a liquid crystal display system.
  • the convention liquid crystal display system comprises a plurality of light tubes to provide light and controls the liquid crystal by using electrodes to let light go through the liquid crystal or not, to display an image.
  • the equivalent resistance of light tubes will gradually decrease and the current going through the light tubes will gradually increase to cause unstable operation of the light tubes and failure to meet the specification.
  • the unstable operation will cause the light tubes to illuminate more than necessary and decrease life time thereof, or to illuminate less than required.
  • the unstable electrical characteristics of the light tubes will cause the liquid crystal display to emit light unstably.
  • the display system comprises an adjusting unit, a pulse generating unit and a light tube.
  • the adjusting unit comprises a thermal resistor and generates an adjusting signal according to environment temperature and a DC voltage.
  • the pulse generating unit generates a pulse driving signal with a first duty cycle according to the adjusting signal.
  • the light tube emits light according to the first duty cycle of the pulse driving signal.
  • the display system comprises an adjusting unit, a pulse width modulation controller, a first driving circuit, a second driving circuit, a first transformer and a light tube.
  • the adjusting unit comprises a thermal resistor and generates an adjusting signal according to environment temperature and a DC voltage.
  • the pulse width modulation controller generates a first pulse signal with a first duty cycle and a second pulse signal with a second duty cycle according to a voltage level of the adjusting signal.
  • the first driving circuit generates a first driving signal according to the first pulse signal.
  • the second driving circuit generates a second driving signal according to the second pulse signal.
  • the first transformer receives the first driving signal and the second driving signal to generate a pulse driving signal with a third duty cycle.
  • the light tube emits light according to the third duty cycle of the pulse driving signal.
  • FIG. 1 is a light tube thermal drift compensation circuit according to an embodiment of the invention
  • FIG. 2 is a light tube thermal drift compensation circuit according to another embodiment of the invention.
  • FIG. 3 is a light tube thermal drift compensation circuit according to another embodiment of the invention.
  • FIG. 4 is a light tube thermal drift compensation circuit according to another embodiment of the invention.
  • FIG. 1 is a light tube thermal drift compensation circuit 100 according to an embodiment of the invention.
  • Compensation circuit 100 can be used in a display system, especially in a liquid crystal display system.
  • Compensation circuit 100 comprises adjusting unit 120 , pulse generating unit 160 and light tubes L 101 and L 102 .
  • Adjusting unit 120 comprises resistors R 121 , R 122 and R 124 , negative temperature coefficient thermal resistor R th1 (i.e. NTC thermistor), and capacitors C 124 and C 122 , as shown in FIG. 1 .
  • Negative temperature coefficient thermal resistor R th1 and resistor R 12 are coupled in parallel and between DC voltage Vcc and node p 1 .
  • Resistor R 122 and capacitor C 122 are individually coupled between node P 1 and ground.
  • Adjusting unit 120 generates adjusting signal S 121 at node P 1 according to resistors R 12 , and R 122 and thermal resistor R th1 .
  • Resistor R 124 and capacitor C 124 are coupled between node P 1 and pulse generating unit 160 for compensation circuit 100 stability.
  • Pulse generating unit 160 comprises pulse width modulation (PWM) controller 170 , driving circuits Q 101 and Q 102 and transformers T 101 and T 102 .
  • Pulse width modulation controller 170 comprises comparator 172 and pulse generator 174 .
  • Comparator 172 compares adjusting signal S 121 to reference voltage V ref1 to generate control signal Ctr 1 .
  • Pulse generator 174 generates pulse signals 182 and 184 according to control signal Ctr 1 .
  • Driving circuits Q 101 and Q 102 respectively receive pulse signals 182 and 184 to generate driving signals 186 and 188 . It is noted that the first phase difference is between pulse signal signals 182 and 184 and the second phase difference is between driving signals 186 and 188 . Normally, the first and second phase differences are the same. Transformers T 101 and T 102 , respectively transform driving signals 186 and 188 into pulse driving signals 192 and 194 to drive light tubes L 101 and L 102 .
  • thermal resistor R th1 can be disposed near pulse generator 160 .
  • thermal resistor R th1 can be disposed near pulse width modulation controller 170 or light tube L 101 or L 102 to detect environment temperature so as to adjust resistance value to change the voltage level of adjusting signal S 121 .
  • environment temperature or internal temperature of compensation circuit 100 rises.
  • thermal resistor R th1 is a negative temperature coefficient thermal resistor in this embodiment, the resistance value of thermal resistor R th1 decreases when environment temperature or internal temperature of compensation circuit 100 rises.
  • the voltage level of adjusting signal S 121 increases and the voltage level of control signal Ctr 1 decreases.
  • Pulse generator 174 generates pulse signals 182 and 184 according to the voltage level of control signal Ctr 1 .
  • the duty cycles of pulse signals 182 and 184 decrease.
  • Driving circuits Q 101 and Q 102 generate driving signals 186 and 188 without changing the duty cycles according to pulse signals 182 and 184 .
  • the duty cycles of driving signals 186 and 188 are the same as those of pulse signals 182 and 184 .
  • Transformers T 101 and T 102 only change the voltage levels but do not change the duty cycles when transformers T 101 and T 102 transform driving signals 186 and 188 into pulse signals 192 and 194 , respectively.
  • the duty cycles of driving signals 186 and 188 decrease and the duty of cycles of pulse signals 192 and 194 also decrease.
  • the emitting light time of light tubes L 101 and L 102 decreases accordingly to reduce heat generation and to decrease the environment temperature.
  • the voltage level of adjusting signal S 121 decreases
  • the voltage level of control signal Ctr 1 increases
  • the duty cycles of pulse signals 182 and 184 increase
  • the duty cycles of driving signals 186 and 188 increase and the duty cycles of pulse signals 192 and 194 also increase.
  • light tubes L 101 and L 102 can be Cold Cathode Fluorescent Lamps (CCFL).
  • CCFL Cold Cathode Fluorescent Lamps
  • FIG. 2 is a light tube thermal drift compensation circuit 200 according to another embodiment of the invention.
  • the difference between compensation circuit 200 and compensation circuit 100 is that compensation circuit 200 only comprises single driving circuit Q 201 , single transformer T 201 and single light tube L 201 .
  • Other components of compensation circuit 200 are the same as those of compensation circuit 100 .
  • the operations of compensation circuits 200 and 100 are substantially the same other than aforementioned difference.
  • Compensation circuit 200 also uses thermal resistor R th1 to detect environment temperature or internal temperature of compensation circuit 200 to control the current going through light tube L 201 to control emitting light time thereof.
  • FIG. 3 is a light tube thermal drift compensation circuit 300 according to another embodiment of the invention.
  • Compensation circuit 300 can be used in a display system, especially in a liquid crystal display system.
  • Compensation circuit 300 comprises adjusting unit 320 , pulse generating unit 360 and light tubes L 301 and L 302 .
  • Adjusting unit 320 comprises resistors R 321 , R 322 and R 324 , negative temperature coefficient thermal resistor R th2 , and capacitors C 324 and C 322 , as shown in FIG. 3 .
  • Negative temperature coefficient thermal resistor R th2 and resistor R 321 are coupled in series and between DC voltage Vcc and node p 2 .
  • Resistor R 322 and capacitor C 322 are coupled between node P 2 and ground.
  • Adjusting unit 320 generates adjusting signal S 321 at node P 2 according to resistors R 321 and R 322 and thermal resistor R th2 .
  • Resistor R 324 and capacitor C 324 are individually coupled between node P 2 and pulse generating unit 360 for compensation circuit 300 stability.
  • Pulse generating unit 360 comprises pulse width modulation (PWM) controller 370 , driving circuits Q 301 and Q 302 and transformers T 301 and T 302 .
  • Pulse width modulation controller 370 comprises comparator 372 and pulse generator 374 . Comparator 372 compares adjusting signal S 321 to reference voltage V ref2 to generate control signal Ctr 2 .
  • Pulse generator 374 generates pulse signals 382 and 384 according to control signal Ctr 2 .
  • Driving circuits Q 301 and Q 302 respectively receive pulse signals 382 and 384 , to generate driving signals 386 and 388 .
  • the third phase difference is between pulse signal signals 382 and 384 .
  • the fourth phase difference is between driving signals 386 and 388 .
  • Transformers T 301 and T 302 respectively transform driving signals 386 and 388 into pulse driving signals 392 and 394 to drive light tubes L 301 and L 302 .
  • FIG. 4 is a light tube thermal drift compensation circuit 400 according to another embodiment of the invention.
  • the difference between compensation circuit 400 and compensation circuit 300 is that compensation circuit 400 only comprises single driving circuit Q 401 , single transformer T401 and single light tube L 401 .
  • Other components of compensation circuit 400 are the same as those of compensation circuit 300 .
  • the operations of compensation circuits 400 and 300 are substantially the same other than aforementioned difference.
  • Compensation circuit 400 also uses thermal resistor R th2 to detect environment temperature and/or internal temperature of compensation circuit 400 to control the current going through light tube L 40 , so as to control emitting light time thereof.
  • thermo resistor it is not limited to use a negative temperature coefficient thermal resistor to detect environment temperature so as to control the current going through the light tube to control emitting light time.
  • a positive temperature coefficient thermal resistor can also work in this invention.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)

Abstract

A display system comprises an adjustment unit, a pulse generating unit and a light tube. The adjustment unit comprises a thermal resistor and generates an adjustment signal according to the temperature. The pulse generating unit generates a pulse driving signal according to the adjusting signal. When the temperature falls, the duty cycle of the pulse driving signal is increased. When the temperature rises, the duty cycle of the pulse driving signal is decreased. The light tube emits light according to the duty cycle of the pulse driving signal.

Description

    BACKGROUND OF THE INVENTION
  • 1. Field of the Invention
  • The invention relates to a display system, and in particular relates to a compensation circuit of a liquid crystal display system.
  • 2. Description of the Related Art
  • The convention liquid crystal display system comprises a plurality of light tubes to provide light and controls the liquid crystal by using electrodes to let light go through the liquid crystal or not, to display an image. However, due to electrical characteristics of light tubes, the equivalent resistance of light tubes will gradually decrease and the current going through the light tubes will gradually increase to cause unstable operation of the light tubes and failure to meet the specification. The unstable operation will cause the light tubes to illuminate more than necessary and decrease life time thereof, or to illuminate less than required. In brief, the unstable electrical characteristics of the light tubes will cause the liquid crystal display to emit light unstably.
  • With regard to manufacturing, due to the unstable electrical characteristics of the light tubes, production yield rate decreases. Alternatively, additional calibration has to be implemented during the manufacturing process to have the current go through the light tubes to meet the desired specification. However, the additional process would also increase manufacturing costs. Thus, solving the problem of the conventional liquid crystal display system which unstably emits light is discussed in this invention.
    • BRIEF SUMMARY OF THE INVENTION
  • A detailed description is given in the following embodiments with reference to the accompanying drawings.
  • An embodiment of a display system is provided. The display system comprises an adjusting unit, a pulse generating unit and a light tube. The adjusting unit comprises a thermal resistor and generates an adjusting signal according to environment temperature and a DC voltage. The pulse generating unit generates a pulse driving signal with a first duty cycle according to the adjusting signal. The light tube emits light according to the first duty cycle of the pulse driving signal.
  • Another embodiment of a display system is provided. The display system comprises an adjusting unit, a pulse width modulation controller, a first driving circuit, a second driving circuit, a first transformer and a light tube. The adjusting unit comprises a thermal resistor and generates an adjusting signal according to environment temperature and a DC voltage. The pulse width modulation controller generates a first pulse signal with a first duty cycle and a second pulse signal with a second duty cycle according to a voltage level of the adjusting signal. The first driving circuit generates a first driving signal according to the first pulse signal. The second driving circuit generates a second driving signal according to the second pulse signal. The first transformer receives the first driving signal and the second driving signal to generate a pulse driving signal with a third duty cycle. The light tube emits light according to the third duty cycle of the pulse driving signal.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
  • FIG. 1 is a light tube thermal drift compensation circuit according to an embodiment of the invention;
  • FIG. 2 is a light tube thermal drift compensation circuit according to another embodiment of the invention;
  • FIG. 3 is a light tube thermal drift compensation circuit according to another embodiment of the invention; and
  • FIG. 4 is a light tube thermal drift compensation circuit according to another embodiment of the invention.
    •  DETAILED DESCRIPTION OF THE INVENTION
  • The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
  • FIG. 1 is a light tube thermal drift compensation circuit 100 according to an embodiment of the invention. Compensation circuit 100 can be used in a display system, especially in a liquid crystal display system. Compensation circuit 100 comprises adjusting unit 120, pulse generating unit 160 and light tubes L101 and L102. Adjusting unit 120 comprises resistors R121, R122 and R124, negative temperature coefficient thermal resistor Rth1 (i.e. NTC thermistor), and capacitors C124 and C122, as shown in FIG. 1. Negative temperature coefficient thermal resistor Rth1 and resistor R12, are coupled in parallel and between DC voltage Vcc and node p1. Resistor R122 and capacitor C122 are individually coupled between node P1 and ground. Adjusting unit 120 generates adjusting signal S121 at node P1 according to resistors R12, and R122 and thermal resistor Rth1. Resistor R124 and capacitor C124 are coupled between node P1 and pulse generating unit 160 for compensation circuit 100 stability. Pulse generating unit 160 comprises pulse width modulation (PWM) controller 170, driving circuits Q101 and Q102 and transformers T101 and T102. Pulse width modulation controller 170 comprises comparator 172 and pulse generator 174. Comparator 172 compares adjusting signal S121 to reference voltage Vref1 to generate control signal Ctr1. Pulse generator 174 generates pulse signals 182 and 184 according to control signal Ctr1. Driving circuits Q101 and Q102, respectively receive pulse signals 182 and 184 to generate driving signals 186 and 188. It is noted that the first phase difference is between pulse signal signals 182 and 184 and the second phase difference is between driving signals 186 and 188. Normally, the first and second phase differences are the same. Transformers T101 and T102, respectively transform driving signals 186 and 188 into pulse driving signals 192 and 194 to drive light tubes L101 and L102.
  • According to an embodiment of the invention, thermal resistor Rth1 can be disposed near pulse generator 160. For example, thermal resistor Rth1 can be disposed near pulse width modulation controller 170 or light tube L101 or L102 to detect environment temperature so as to adjust resistance value to change the voltage level of adjusting signal S121. Following an operating period of compensation circuit 100, environment temperature or internal temperature of compensation circuit 100 rises. Since thermal resistor Rth1 is a negative temperature coefficient thermal resistor in this embodiment, the resistance value of thermal resistor Rth1 decreases when environment temperature or internal temperature of compensation circuit 100 rises. The voltage level of adjusting signal S121 increases and the voltage level of control signal Ctr1 decreases. Pulse generator 174 generates pulse signals 182 and 184 according to the voltage level of control signal Ctr1. When the voltage level of control signal Ctr1 decreases because of temperature rise, the duty cycles of pulse signals 182 and 184 decrease. Driving circuits Q101 and Q102 generate driving signals 186 and 188 without changing the duty cycles according to pulse signals 182 and 184. Thus, the duty cycles of driving signals 186 and 188 are the same as those of pulse signals 182 and 184. Transformers T101 and T102 only change the voltage levels but do not change the duty cycles when transformers T101 and T102 transform driving signals 186 and 188 into pulse signals 192 and 194, respectively. When environment temperature rises, the duty cycles of driving signals 186 and 188 decrease and the duty of cycles of pulse signals 192 and 194 also decrease. Thus, the emitting light time of light tubes L101 and L102 decreases accordingly to reduce heat generation and to decrease the environment temperature. According to another embodiment of the invention, when the currents going through light tubes L101 and L102 decrease, the illumination and heat of light tubes L101 and L102 decreases and the environment temperature falls, Thus, the voltage level of adjusting signal S121 decreases, the voltage level of control signal Ctr1 increases, the duty cycles of pulse signals 182 and 184 increase, the duty cycles of driving signals 186 and 188 increase and the duty cycles of pulse signals 192 and 194 also increase. Consequently, the emitting light time of light tubes L101 and L102 increases to improve the problem that light tubes L101 and L102 may not be illuminated enough. Meanwhile, light tubes L101 and L102 can be Cold Cathode Fluorescent Lamps (CCFL).
  • FIG. 2 is a light tube thermal drift compensation circuit 200 according to another embodiment of the invention. The difference between compensation circuit 200 and compensation circuit 100 is that compensation circuit 200 only comprises single driving circuit Q201, single transformer T201 and single light tube L201. Other components of compensation circuit 200 are the same as those of compensation circuit 100. The operations of compensation circuits 200 and 100 are substantially the same other than aforementioned difference. Compensation circuit 200 also uses thermal resistor Rth1 to detect environment temperature or internal temperature of compensation circuit 200 to control the current going through light tube L201 to control emitting light time thereof.
  • FIG. 3 is a light tube thermal drift compensation circuit 300 according to another embodiment of the invention. Compensation circuit 300 can be used in a display system, especially in a liquid crystal display system. Compensation circuit 300 comprises adjusting unit 320, pulse generating unit 360 and light tubes L301 and L302. Adjusting unit 320 comprises resistors R321, R322 and R324, negative temperature coefficient thermal resistor Rth2, and capacitors C324 and C322, as shown in FIG. 3. Negative temperature coefficient thermal resistor Rth2 and resistor R321 are coupled in series and between DC voltage Vcc and node p2. Resistor R322 and capacitor C322 are coupled between node P2 and ground. Adjusting unit 320 generates adjusting signal S321 at node P2 according to resistors R321 and R322 and thermal resistor Rth2. Resistor R324 and capacitor C324 are individually coupled between node P2 and pulse generating unit 360 for compensation circuit 300 stability. Pulse generating unit 360 comprises pulse width modulation (PWM) controller 370, driving circuits Q301 and Q302 and transformers T301 and T302. Pulse width modulation controller 370 comprises comparator 372 and pulse generator 374. Comparator 372 compares adjusting signal S321 to reference voltage Vref2 to generate control signal Ctr2. Pulse generator 374 generates pulse signals 382 and 384 according to control signal Ctr2. Driving circuits Q301 and Q302 respectively receive pulse signals 382 and 384, to generate driving signals 386 and 388. The third phase difference is between pulse signal signals 382 and 384. The fourth phase difference is between driving signals 386 and 388. Normally, the third and fourth phase differences are the same. Transformers T301 and T302, respectively transform driving signals 386 and 388 into pulse driving signals 392 and 394 to drive light tubes L301 and L302.
  • FIG. 4 is a light tube thermal drift compensation circuit 400 according to another embodiment of the invention. The difference between compensation circuit 400 and compensation circuit 300 is that compensation circuit 400 only comprises single driving circuit Q401, single transformer T401 and single light tube L401. Other components of compensation circuit 400 are the same as those of compensation circuit 300. The operations of compensation circuits 400 and 300 are substantially the same other than aforementioned difference. Compensation circuit 400 also uses thermal resistor Rth2 to detect environment temperature and/or internal temperature of compensation circuit 400 to control the current going through light tube L40, so as to control emitting light time thereof.
  • It is not limited to use a negative temperature coefficient thermal resistor to detect environment temperature so as to control the current going through the light tube to control emitting light time. A positive temperature coefficient thermal resistor can also work in this invention.
  • While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited to thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Claims (20)

1. A display system, comprising
an adjusting unit, comprising a thermal resistor with a resistance value and generating an adjusting signal with a first voltage level according to a temperature;
a pulse generating unit, generating a pulse driving signal with a first duty cycle according to the adjusting signal; and
a light tube, emitting light according to the first duty cycle of the pulse driving signal.
2. The display system as claimed in claim 1, wherein when the first duty cycle of the pulse driving signal increases, a emitting light time of the light tube increases and when the first duty cycle of the pulse driving signal decreases, the emitting light time of the light tube decreases.
3. The display system as claimed in claim 1, wherein the light tube is used in a liquid crystal display system.
4. The display system as claimed in claim 1, wherein the adjusting unit comprises:
a first resistor, coupled to the thermal resistor in parallel; and
a second resistor, coupled between the ground and the thermal resistor.
5. The display system as claimed in claim 1, wherein the adjusting unit comprises:
a first resistor, coupled to the thermal resistor in series; and
a second resistor, coupled between the ground and the thermal resistor.
6. The display system as claimed in claim 1, wherein the thermal resistor adjusts the resistance value according to the temperature to adjust the first voltage level of the adjusting signal.
7. The display system as claimed in claim 6, wherein when the temperature falls, the thermal resistor changes the resistance value to decrease the first voltage level of the adjusting signal for increasing the first duty cycle of the pulse driving signal, and when the temperature rises, the thermal resistor changes the resistance value to increase the first voltage level of the adjusting signal for decreasing the first duty cycle of the pulse driving signal.
8. The display system as claimed in claim 1, wherein the pulse generating unit comprises:
a pulse width modulation controller, generating a pulse signal with a second duty cycle according to the first voltage level of the adjusting signal;
a driving circuit, generating a driving signal according to the pulse signal; and
a transformer, converting the pulse signal into the pulse driving signal;
wherein when the temperature falls, the first voltage level of the adjusting signal decreases to increase the second duty cycle of the pulse signal and the first duty cycle of the pulse driving signal, and when the temperature rises, the first voltage level of the adjusting signal increases to decrease the second duty cycle of the pulse signal and the first duty cycle of the pulse driving signal.
9. The display system as claimed in claim 8, wherein the pulse width modulation controller comprises:
a comparator, comparing the first voltage level of the adjusting signal to a reference voltage to generate a control signal with a second voltage level; and
a pulse generator, generating the pulse signal according to the control signal;
wherein when the temperature falls, the first voltage level of the adjusting signal decreases and the second voltage level of the control signal increases to increase the second duty cycle of the pulse signal, and when the temperature rises, the first voltage level of the adjusting signal increases and the second voltage level of the control signal decreases to decrease the second duty cycle of the pulse signal.
10. The display system as claimed in claim 8, wherein the thermal resistor is disposed near at least one of the pulse width modulation controller or the light tube to detect the temperature.
11. A display system, comprising
an adjusting unit, comprising a thermal resistor with a resistance value and generating an adjusting signal with a first voltage level according to a temperature;
a pulse width modulation controller, generating a first pulse signal with a first duty cycle and a second pulse signal with a second duty cycle according to the first voltage level of the adjusting signal;
a first driving circuit, generating a first driving signal according to the first pulse signal;
a second driving circuit, generating a second driving signal according to the second pulse signal;
a first transformer, receiving the first driving signal and the second driving signal to generate a pulse driving signal with a third duty cycle; and
a light tube, emitting light according to the third duty cycle of the pulse driving signal.
12. The display system as claimed in claim 11, wherein when the third duty cycle of the pulse driving signal increases, a emitting light time of the light tube increases and when the third duty cycle of the pulse driving signal decreases, the emitting light time of the light tube decreases.
13. The display system as claimed in claim 11, wherein the light tube is used in a liquid crystal display system.
14. The display system as claimed in claim 11, wherein the adjusting unit comprises:
a first resistor, coupled to the thermal resistor in parallel; and
a second resistor, coupled between ground and the thermal resistor.
15. The display system as claimed in claim 11, wherein the adjusting unit comprises:
a first resistor, coupled to the thermal resistor in series; and
a second resistor, coupled between ground and the thermal resistor.
16. The display system as claimed in claim 11, wherein the thermal resistor adjusts the resistance value according to the temperature to adjust the first voltage level of the adjusting signal.
17. The display system as claimed in claim 11, wherein when the temperature falls, the thermal resistor changes the resistance value to decrease the first voltage level of the adjusting signal for increasing the third duty cycle of the pulse driving signal, and when the temperature rises, the thermal resistor changes the resistance value to increase the first voltage level of the adjusting signal for decreasing the third duty cycle of the pulse driving signal.
18. The display system as claimed in claim 11, wherein the pulse width modulation controller comprises:
a comparator, comparing the first voltage level of the adjusting signal to a reference voltage to generate a control signal with a second voltage level; and
a pulse generator, generating the first pulse signal and the second pulse signal according to the control signal;
wherein when the temperature falls, the first voltage level of the adjusting signal decreases and the second voltage level of the control signal increases to increase the first duty cycle of the first pulse signal, the second duty cycle of the second pulse signal and the third duty cycle of the pulse driving signal, and when the temperature rises, the first voltage level of the adjusting signal increases and the second voltage level of the control signal decreases to decrease the first duty cycle of the first pulse signal, the second duty cycle of the second pulse signal and the third duty cycle of the pulse driving signal.
19. The display system as claimed in claim 11, wherein the thermal resistor is disposed near at least one of the pulse width modulation controller or the light tube to detect the temperature.
20. The display system as claimed in claim 11, wherein the thermal resistor is a negative temperature coefficient thermal resistor.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100141672A1 (en) * 2008-12-09 2010-06-10 Samsung Electronics Co. Ltd. Light source device, display apparatus having the light source device and method of driving the light source device
US10395596B2 (en) * 2016-12-28 2019-08-27 Lg Display Co., Ltd. Organic light emitting display device, data driver, and method for driving data driver
CN110379373A (en) * 2019-06-14 2019-10-25 昆山龙腾光电有限公司 Backlight drive circuit and its control method and liquid crystal display device
CN111525793A (en) * 2020-04-17 2020-08-11 Tcl华星光电技术有限公司 Power circuit, display panel using same and dynamic adjustment method

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6693394B1 (en) * 2002-01-25 2004-02-17 Yazaki North America, Inc. Brightness compensation for LED lighting based on ambient temperature
US20070057902A1 (en) * 2005-09-09 2007-03-15 Samsung Electro-Mechanics Co., Ltd. Circuit for controlling LED with temperature compensation
US7425800B2 (en) * 2006-02-10 2008-09-16 Hon Hai Precision Industry Co., Ltd. Device for driving a light source module

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6693394B1 (en) * 2002-01-25 2004-02-17 Yazaki North America, Inc. Brightness compensation for LED lighting based on ambient temperature
US20070057902A1 (en) * 2005-09-09 2007-03-15 Samsung Electro-Mechanics Co., Ltd. Circuit for controlling LED with temperature compensation
US7425800B2 (en) * 2006-02-10 2008-09-16 Hon Hai Precision Industry Co., Ltd. Device for driving a light source module

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100141672A1 (en) * 2008-12-09 2010-06-10 Samsung Electronics Co. Ltd. Light source device, display apparatus having the light source device and method of driving the light source device
US8605030B2 (en) * 2008-12-09 2013-12-10 Samsung Display Co., Ltd. Method of preventing the temperature of a backlight source from remaining at a low temperature based on the duty ratio history of the backlight
US9439266B2 (en) 2008-12-09 2016-09-06 Samsung Display Co., Ltd. Method for adjusting pixel data based on the duty ratio history of the backlight in order to compensate for the temperature of the backlight
US10395596B2 (en) * 2016-12-28 2019-08-27 Lg Display Co., Ltd. Organic light emitting display device, data driver, and method for driving data driver
CN110379373A (en) * 2019-06-14 2019-10-25 昆山龙腾光电有限公司 Backlight drive circuit and its control method and liquid crystal display device
CN111525793A (en) * 2020-04-17 2020-08-11 Tcl华星光电技术有限公司 Power circuit, display panel using same and dynamic adjustment method

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